High Density Lipoprotein Fraction Research Articles

An assessment of the (anti)androgenic properties of hexachloronaphthalene (HxCN) in male rats

The persistent organic pollutants (POPs) defined by the Stockholm Convention include polychlorinated naphthalenes (PCNs); of these, the most toxic, persistent, abundant, dioxin-like congeners found in human tissues are the hexachloronaphthalenes (HxCNs). Recent research also indicates that PCNs may disrupt hormonal homeostasis. The aim of this study was to evaluate the (anti)androgenic action of HxCN. Immature, castrated male Wistar rats were exposed per os to HxCN in corn oil at daily doses ranging from 0.3-3.0 mg kg-1 for 10 days. According to the OECD 441 protocol (Hershberger Bioassay), the anti-androgenic assay groups were co-exposed with testosterone propionate (TP), while the androgenic groups were not. TP was used as the reference androgen (subcutaneous daily doses of 0.4 mg kg-1), and flutamide (FLU) as the reference antiandrogen (per os daily doses of 3.0 mg kg-1). Five assessor sex tissues (ASTs) were weighed: ventral prostate, seminal vesicles, levator ani-bulbocavernosus muscle (LABC), Cowper’s glands and glans penis. HxCN + TP significantly decreased the weight of the ventral prostate and seminal vesicle indicating an anti-androgenic action via 5α-reductase inhibition. These weight changes were also accompanied by abnormalities in cell morphology and hormonal disturbances: lowered levels of the testosterone and thyroid hormones thyroxine and triiodothyronine. Disturbances were also noted in the lipid profile, viz. total cholesterol, triglycerides and high-density lipoprotein and non-HDL fraction content. However, the direction of these changes differed depending on the size of the HxCN dose. No dose-effect relationship was noted for most of the obtained results; as such, exposure to even small HxCN doses run the risk of anti-androgenic effects in the general population, especially when encountered in combination with other POPs and endocrine-disrupting chemicals in the environment.

Cholesterol-Lowering and Antioxidant Effects of Pork-Liver Protein Hydrolysate in Otsuka Long-Evans Tokushima Fatty Rats.

In this study, we investigated the effects of a porcine liver protein hydrolysate (PLH) diet on lipid metabolism in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of type II diabetes. OLETF rats (20-wk-old males) were pair-fed with either a PLH diet containing 20% PLH or a casein diet for 14 wk. Dietary PLH significantly lowered serum cholesterol and phospholipid concentrations, mainly by decreasing low-density lipoprotein and high-density lipoprotein fractions. Fecal cholesterol was significantly increased in the PLH diet group; however, the total bile acid concentration in the feces was not significantly different between the groups. In addition, the PLH diet significantly decreased serum thiobarbituric acid reactive substance concentrations. These results suggest that dietary PLH exerts hyperlipidemic and antioxidant effects, indicating that it is a novel functional food ingredient.

Functionalisation of brush polyethylene glycol polymers with specific lipids extends their elimination half-life through association with natural lipid trafficking pathways

Polymeric prodrugs have been applied to control the delivery of various types of therapeutics. Similarly, conjugation of peptide therapeutics to lipids has been used to prolong systemic exposure. Here, we extend on these two approaches by conjugating brush polyethylene glycol (PEG) polymers with different lipid components including short-chain (1C2) or medium-chain (1C12) monoalkyl hydrocarbon tails, cholesterol (Cho), and diacylglycerols composed of two medium-chain (2C12) or long-chain (2C18) fatty acids. We uniquely evaluate the integration of these lipid-polymers into endogenous lipid trafficking pathways (albumin and lipoproteins) and the impact of lipid conjugation on plasma pharmacokinetics after intravenous (IV) and subcutaneous (SC) dosing to cannulated rats. The IV and SC elimination half-lives of Cho-PEG (13 and 22 h, respectively), 2C12-PEG (11 and 17 h, respectively) and 2C18-PEG (12 h for both) were prolonged compared to 1C2-PEG (3 h for both) and 1C12-PEG (4 h for both). Interestingly, 1C2-PEG and 1C12-PEG had higher SC bioavailability (40 % and 52 %, respectively) compared to Cho-PEG, 2C12-PEG and 2C18-PEG (25 %, 24 % and 23 %, respectively). These differences in pharmacokinetics may be explained by the different association patterns of the polymers with rat serum albumin (RSA), bovine serum albumin (BSA) and lipoproteins. For example, in pooled plasma (from IV pharmacokinetic studies), 2C18-PEG had the highest recovery in the high-density lipoprotein (HDL) fraction. In conclusion, the pharmacokinetics of brush PEG polymers can be tuned via conjugation with different lipids, which can be utilised to tune the elimination half-life, biodistribution and effect of therapeutics for a range of medical applications. Statement of significanceLipidation of therapeutics such as peptides has been employed to extend their plasma half-life by promoting binding to serum albumin, providing protection against rapid clearance. Here we design and evaluate innovative biomaterials consisting of brush polyethylene glycol polymers conjugated with different lipids. Importantly, we show for the first time that lipidated polymeric materials associate with endogenous lipoprotein trafficking pathways and this, in addition to albumin binding, controls their plasma pharmacokinetics. We find that conjugation to dialkyl lipids and cholesterol leads to higher association with lipid trafficking pathways, and more sustained plasma exposure, compared to conjugation to short and monoalkyl lipids. Our lipidated polymers can thus be utilised as delivery platforms to tune the plasma half-life of various pharmaceuticals.

Analysis of vitamin K1 and major K2 variants in rat/human serum and lipoprotein fractions by a rapid, simple, and sensitive UHPLC-MS/MS method

Determination of the various forms of vitamin K, which are involved in coagulation and other physiological processes in humans, is challenging and no standardized method is yet available. Therefore, a reliable and practical method was developed to quantify vitamin K levels in serum and additionally in lipoprotein fractions to clarify its distribution. The LC-MS/MS method for the determination of vitamin K1 and the three main isoforms of vitamin K2 (MK-4, MK-7, MK-9) was combined with a gradient ultracentrifugation technique to allow the separation of lipoprotein fractions. The chromatographic separation was carried out on a Kinetex™ C18 column using a mobile phase consisting mainly of methanol. The target analytes were detected by electrospray ionization mass spectrometry. The separation of all four substances was achieved after a simple sample preparation technique based on miniaturized liquid-liquid extraction. Our method of only 8.5 min revealed the levels of the major forms of vitamin K in 59 human and 12 rat sera and confirmed our hypothesis that vitamin K is primarily (about 50 %) found in the high-density lipoprotein fraction. The median concentrations of vitamin K1, MK-4, MK-7, and MK-9 were found to be 1.19, 2.98, 0.43, and < 0.71 nmol/L in human serum and 1.74, 6.75, less than 0.2, and less than 0.5 nmol/L in rat serum, respectively.

ANGPTL3 (Angiopoietin-Like 3) Preferentially Resides on High-Density Lipoprotein in the Human Circulation, Affecting Its Activity.

Background ANGPTL3 (angiopoietin-like protein 3) is an acknowledged crucial regulator of lipid metabolism by virtue of its inhibitory effect on lipoprotein lipase and endothelial lipase. It is currently unknown whether and to which lipoproteins ANGPTL3 is bound and whether the ability of ANGPTL3 to inhibit lipase activity is affected by binding to lipoproteins. Methods and Results Incubation of ultracentrifugation-isolated low-density lipoprotein (LDL) and high-density lipoprotein (HDL) fractions from healthy volunteers with recombinant ANGPTL3 revealed that ANGPTL3 associates with both HDL and LDL particles ex vivo. Plasma from healthy volunteers and a patient deficient in HDL was fractionated by fast protein liquid chromatography, and ANGPTL3 distribution among lipoprotein fractions was measured. In healthy volunteers, ≈75% of lipoprotein-associated ANGPTL3 resides in HDL fractions, whereas ANGPTL3 was largely bound to LDL in the patient deficient in HDL. ANGPTL3 activity was studied by measuring lipolysis and uptake of 3H-trioleate by brown adipocyte T37i cells. Unbound ANGPTL3 did not suppress lipase activity, but when given with HDL or LDL, ANGPTL3 suppressed lipase activity by 21.4±16.4% (P=0.03) and 25.4±8.2% (P=0.006), respectively. Finally, in a subset of the EPIC (European Prospective Investigation into Cancer) Norfolk study, plasma HDL cholesterol and amount of large HDL particles were both positively associated with plasma ANGPTL3 concentrations. Moreover, plasma ANGPTL3 concentrations showed a positive association with incident coronary artery disease (odds ratio, 1.25 [95% CI, 1.01-1.55], P=0.04). Conclusions Although ANGPTL3 preferentially resides on HDL, its activity was highest once bound to LDL particles.

Triglyceride content increases while cholesterol content decreases in HDL and LDL+IDL fractions following normal meals: The Copenhagen General Population Study of 25,656 individuals

Background and aimsDuring fat tolerance tests, plasma triglycerides increase while high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and intermediate-density lipoprotein (IDL) cholesterol decrease. However, it is unknown whether triglyceride content increases and cholesterol content decreases in HDL and LDL + IDL fractions following normal meals in the general population. Therefore, we tested the hypothesis that triglyceride content increases while cholesterol content decreases in HDL and LDL + IDL fractions following normal meals. MethodsIn this cross-sectional study, we included 25,656 individuals aged 20–100 years, all without lipid-lowering therapy at examination and selected for metabolomic profiling from the Copenhagen General Population Study. Triglyceride and cholesterol content of 14 lipoprotein fractions weas measured using nuclear magnetic resonance (NMR) spectroscopy. Time since last meal was recorded by the examiner immediately before blood sampling. ResultsFollowing normal meals in age and sex-adjusted analyses and when compared with fasting levels, plasma triglycerides were higher for up to 5–6 h, and triglyceride content was higher for up to 6–7 h in HDL fractions, for up to 6–7 h in LDL + IDL fractions, and for up to 5–6 h in very-low-density lipoprotein (VLDL) fractions. Further, plasma cholesterol was lower for up to 2–3 h, and cholesterol content was lower for up to 0–1 h in HDL fractions and for up to 4–5 h in LDL + IDL fractions, while cholesterol content was higher for up to 4–5 h in VLDL fractions. ConclusionsFollowing normal meals, triglyceride content increases while cholesterol content decreases in HDL and LDL + IDL fractions.

Hepatic SREBP signaling requires SPRING to govern systemic lipid metabolism in mice and humans

The sterol regulatory element binding proteins (SREBPs) are transcription factors that govern cholesterol and fatty acid metabolism. We recently identified SPRING as a post-transcriptional regulator of SREBP activation. Constitutive or inducible global ablation of Spring in mice is not tolerated, and we therefore develop liver-specific Spring knockout mice (LKO). Transcriptomics and proteomics analysis reveal attenuated SREBP signaling in livers and hepatocytes of LKO mice. Total plasma cholesterol is reduced in male and female LKO mice in both the low-density lipoprotein and high-density lipoprotein fractions, while triglycerides are unaffected. Loss of Spring decreases hepatic cholesterol and triglyceride content due to diminished biosynthesis, which coincides with reduced very-low-density lipoprotein secretion. Accordingly, LKO mice are protected from fructose diet-induced hepatosteatosis. In humans, we find common genetic SPRING variants that associate with circulating high-density lipoprotein cholesterol and ApoA1 levels. This study positions SPRING as a core component of hepatic SREBP signaling and systemic lipid metabolism in mice and humans.

Serum proteomic identification and validation of two novel atherosclerotic aortic aneurysm biomarkers, profilin 1 and complement factor D

BackgroundEffective diagnostic biomarkers for aortic aneurysm (AA) that are detectable in blood tests are required because early detection and rupture risk assessment of AA can provide insights into medical therapy and preventive treatments. However, known biomarkers for AA lack specificity and reliability for clinical diagnosis.MethodsWe performed proteome analysis of serum samples from patients with atherosclerotic thoracic AA (TAA) and healthy control (HC) subjects to identify diagnostic biomarkers for AA. Serum samples were separated into low-density lipoprotein, high-density lipoprotein, and protein fractions, and the major proteins were depleted. From the proteins identified in the three fractions, we narrowed down biomarker candidates to proteins uniformly altered in all fractions between patients with TAA and HC subjects and evaluated their capability to discriminate patients with TAA and those with abdominal AA (AAA) from HC subjects using receiver operating characteristic (ROC) analysis. For the clinical validation, serum concentrations of biomarker candidates were measured in patients with TAA and AAA registered in the biobank of the same institute, and their capability for the diagnosis was evaluated.ResultsProfilin 1 (PFN1) and complement factor D (CFD) showed the most contrasting profiles in all three fractions between patients with TAA and HC subjects and were selected as biomarker candidates. The PFN1 concentration decreased, whereas the CFD concentration increased in the sera of patients with TAA and AAA when compared with those of HC subjects. The ROC analysis showed that these proteins could discriminate patients with TAA and AAA from HC subjects. In the validation study, these candidates showed significant concentration differences between patients with TAA or AAA and controls. PFN1 and CFD showed sufficient area under the curve (AUC) in the ROC analysis, and their combination further increased the AUC. The serum concentrations of PFN1 and CFD also showed significant differences between patients with aortic dissection and controls in the validation study.ConclusionPFN1 and CFD are potential diagnostic biomarkers for TAA and AAA and measurable in blood samples; their diagnostic performance can be augmented by their combination. These biomarkers may facilitate the development of diagnostic systems to identify patients with AA.

Abnormal Lipoproteins Trigger Oxidative Stress-Mediated Apoptosis of Renal Cells in LCAT Deficiency.

Familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare genetic disease caused by the loss of function mutations in the LCAT gene. LCAT deficiency is characterized by an abnormal lipoprotein profile with severe reduction in plasma levels of high-density lipoprotein (HDL) cholesterol and the accumulation of lipoprotein X (LpX). Renal failure is the major cause of morbidity and mortality in FLD patients; the pathogenesis of renal disease is only partly understood, but abnormalities in the lipoprotein profile could play a role in disease onset and progression. Serum and lipoprotein fractions from LCAT deficient carriers and controls were tested for renal toxicity on podocytes and tubular cells, and the underlying mechanisms were investigated at the cellular level. Both LpX and HDL from LCAT-deficient carriers triggered oxidative stress in renal cells, which culminated in cell apoptosis. These effects are partly explained by lipoprotein enrichment in unesterified cholesterol and ceramides, especially in the HDL fraction. Thus, alterations in lipoprotein composition could explain some of the nephrotoxic effects of LCAT deficient lipoproteins on podocytes and tubular cells.

ApoA-I and Diabetes.

ApoA-I-the main apolipoprotein constituent of the HDL (high-density lipoprotein) fraction of human plasma-is of therapeutic interest because it has several cardioprotective functions. Recent reports have established that apoA-I also has antidiabetic properties. In addition to improving glycemic control by increasing insulin sensitivity, apoA-I improves pancreatic β-cell function by amplifying expression of transcription factors that are essential for β-cell survival and increasing insulin production and secretion in response to a glucose challenge. These findings indicate that increasing circulating apoA-I levels may be of therapeutic value in patients with diabetes in whom management of glycemic control is suboptimal. This review summarizes current knowledge of the antidiabetic functions of apoA-I and the mechanistic basis of these effects. It also evaluates the therapeutic potential of small, clinically relevant peptides that mimic the antidiabetic functions of full-length apoA-I and describes potential strategies for development of these peptides into innovative options for treatment of diabetes.

Preparative Electrophoresis for HDL Particle Size Separation and Intact-Mass Apolipoprotein Proteoform Analysis.

The most abundant proteins on high-density lipoproteins (HDLs), apolipoproteins A-I (APOA1) and A-II (APOA2), are determinants of HDL function with 15 and 9 proteoforms (chemical-structure variants), respectively. The relative abundance of these proteoforms in human serum is associated with HDL cholesterol efflux capacity, and cholesterol content. However, the association between proteoform concentrations and HDL size is unknown. We employed a novel native-gel electrophoresis technique, clear native gel-eluted liquid fraction entrapment electrophoresis (CN-GELFrEE) paired with mass spectrometry of intact proteins to investigate this association. Pooled serum was fractionated using acrylamide gels of lengths 8 and 25 cm. Western blotting determined molecular diameter and intact-mass spectrometry determined proteoform profiles of each fraction. The 8- and 25 cm experiments generated 19 and 36 differently sized HDL fractions, respectively. The proteoform distribution varied across size. Fatty-acylated APOA1 proteoforms were associated with larger HDL sizes (Pearson's R = 0.94, p = 4 × 10-7) and were approximately four times more abundant in particles larger than 9.6 nm than in total serum; HDL-unbound APOA1 was acylation-free and contained the pro-peptide proAPOA1. APOA2 proteoform abundance was similar across HDL sizes. Our results establish CN-GELFrEE as an effective lipid-particle separation technique and suggest that acylated proteoforms of APOA1 are associated with larger HDL particles.

Effects of Dietary Halloysite Supplementation on Broiler Chicken’s Blood Parameters, Carcass and Meat Quality, and Bone Characteristics: A Preliminary Study

Abstract The aim of this study was to determine the effect of halloysite supplementation to the complete diets for broiler chickens on selected blood parameters, carcass and organ characteristics, as well as bone and meat traits. The trial was conducted under experimental conditions in a large-scale poultry farm on 18,000 broiler chickens. The one-day broiler Ross 308 chicks were randomly divided into two groups: control (C) and experimental (E) in an amount of 9,000 birds per group. In each group, chicks were separated into five pens (100 m2) with 1800 chicks per pen. The birds were fed granulated complete mixtures without (C group) or with halloysite (E group) distributed in an amount of 1% (based on fresh matter) from the 11 d of life. Analysis revealed that halloysite supplementation to the broiler diet at the level of 1% showed a trend (P = 0.056) towards higher final body weight, significantly improved carcass yield (P = 0.048), and reduced the relative weights of the liver and gizzard (P&lt;0.05). No differences (P&gt;0.05) were observed either in terms of the physicochemical parameters of the broiler chickens’ breast muscles, except a significantly lower b* value of the colour parameter (P = 0.048). In turn, in the blood serum, the addition of 1% halloysite significantly decreased (P&lt;0.05) the content of triglycerides and the total cholesterol and low-density lipoprotein fraction, but did not affect (P&gt;0.05) the high-density lipoprotein fraction, calcium, phosphorus or alkaline phosphate content. Tibia and femur characteristics (weight, length, relative bone weight, bone mineral density, bone mineral content, and breaking strength) were not affected (P&gt;0.05) by the usage of halloysite. In conclusion, supplementation of broiler diet with halloysite in the amount of 1% had beneficial effects on the carcass yield and health status of the animals, without any adverse effect on the bone parameters or meat quality of the broiler chickens.

Comparative Susceptibility to Oxidation of Different Classes of Blood Plasma Lipoproteins.

The kinetics of free radical peroxidation of different classes of blood plasma lipoproteins (nanoparticles involved in lipid transport in the body) was studied. The susceptibility of atherogenic low-density lipoproteins (LDLs) to the Cu2+-initiated free radical peroxidation in vitro was found to be more than ten times higher than that of antiatherogenic high density lipoproteins (HDLs). The baseline content of acyl hydroperoxy derivatives of phospholipids (primary products of free radical peroxidation) in the outer layer of LDL particles in vivo measured per particle exceeded the baseline content of these compounds in HDL particles by more than an order of magnitude. The susceptibility to oxidation of the HDL2 subfraction of HDLs was higher than the susceptibility of total HDL fraction and HDL3 subfraction. The data obtained confirm an important role of free radical peroxidation of LDLs in the molecular mechanisms of vascular wall damage in atherosclerosis.

Characteristics of lipid spectrum and functional liver tests in patients with nonalcoholic liver steatosis depending on degree of obesity during menopause

Objective. To study the blood lipid spectrum and functional liver tests in women with nonalcoholic liver steatosis (NALS) depending on the degree of obesity during menopause.&#x0D; Materials and methods. Seventy patients with NALS and obesity (NALS-O-M) in menopause with the mean age of 49,9 1,1 years including 24 with increased body mass index (BMI), 20 with the degree 1 obesity, 18 the degree 2 obesity and 8 the degree 3 obesity were examined. The control group involved 30 practically healthy women in menopause without obesity. Blood serum cytolysis, cholestasis and lipid spectrum indicators were studied in both groups.&#x0D; Results. According to the results of biochemical investigation, in the group of patients with NALS-O-M syndrome no cytolysis was observed. In case of marked obesity, cholestasis syndrome by the blood alkaline phosphatase level was identified. Lipid spectrum in patients with NALS-O-M statistically significantly differed from the control: hypercholesterinemia, hypertriglyceridemia, increase in the low- and very low-density lipoproteins as well as calculated index of atherogeneity with decrease in the high-density lipoproteins fraction was registered.&#x0D; Conclusions. A pronounced obesity causes the cholestasis syndrome with an increase in the blood alkaline phosphatase level. Dyslipidemia of different degree of manifestation is registered in all patients with steatosis and obesity during menopause, being more marked in patients with the degree 23 obesity.

Lipid Profile, Lp(a) Levels, and HDL Quality in Adolescents with Down Syndrome.

The improvement in the lifespan of individuals with Down syndrome (DS) has created interest in the context of the development of age-related diseases. Among them is atherosclerosis-based cardiovascular disease (CVD), which seems to be an especially urgent and important issue. The aim of the present study was to evaluate the lipid markers that may clarify cardiovascular risk profiles in individuals with DS. To this end, we analyzed lipid profile parameters, including lipoprotein(a) (Lp(a)) levels, protein composition, and the antioxidative properties of high-density lipoprotein (HDL), in 47 adolescents with DS and 47 individuals without DS. Compared with the control group (C), subjects with DS had significantly increased concentrations of low-density lipoprotein cholesterol (105 ± 31 vs. 90 ± 24 mg/dL, p = 0.014), non-high-density lipoprotein cholesterol (120 ± 32 vs. 103 ± 26 mg/dL, p = 0.006), and triglycerides (72 [55–97] vs. 60 [50–77] mg/dL, p = 0.048). We found that patients with DS were characterized by significantly higher Lp(a) levels (31.9 [21.5–54.3] vs. 5.2 (2.4–16.1) mg/dL, p < 0.001). In fact, 57% of individuals with DS had Lp(a) levels above 30 mg/dL, which was approximately four times higher than those in the control group (DS 57% vs. C 15%). Apart from decreased high-density lipoprotein cholesterol levels in the subjects with DS (53 ± 11 vs. 63 ± 12 mg/dL, p < 0.001), differences in parameters showing the quality of HDL particles were observed. The concentrations of the main proteins characterizing the HDL fraction, apolipoprotein A-I and apolipoprotein A-II, were significantly lower in the DS group (144 ± 21 vs. 181 ± 33 mg/dL, p < 0.001; 33 ± 6 vs. 39 ± 6 mg/dL, p < 0.001, respectively). No significant differences between the groups were observed for the concentration of paraoxonase-1 (DS 779 ± 171 vs. C 657 ± 340 ng/mL, p = 0.063), enzyme activities toward paraoxon (DS 219 [129–286] vs. C 168 [114–272] IU/L, p = 0.949), or phenyl acetate (DS 101 ± 20 vs. C 93 ± 21 kIU/L, p = 0.068). There were no differences in myeloperoxidase activity between the study groups (DS 327 [300–534] vs. C 426 [358–533] ng/mL, p = 0.272). Our results are the first to demonstrate an unfavorable lipid profile combined with higher Lp(a) levels and quality changes in HDL particles in individuals with DS. This sheds new light on cardiovascular risk and traditional healthcare planning for adolescents with DS.

Agarose gel electrophoresis determination of bovine lipoproteins compared with a wet chemistry method

Quantification of serum lipoproteins provides information relative to the overall metabolic health, degree of lipid mobilization, and hepatic function of dairy cattle. Automated assays performed on benchtop chemistry analyzers and commercially available kits use reagents developed for human lipoproteins. The substantial physical and chemical differences between bovine and human lipoproteins potentially confounds the use of these assays in evaluating bovine lipoproteins. In this study, we prospectively analyzed serum lipoproteins from 56 Holstein cows using horizontal slab agarose gel electrophoresis to semi-quantify the high-density lipoprotein (HDL) and low-density lipoprotein (LDL) fractions by optical densitometry. Ultracentrifugation was used to confirm the electrophoretic separation pattern of the lipoproteins. The values obtained using the electrophoretic method were compared with values obtained by direct measure of HDL cholesterol, total cholesterol, and triglyceride (TG) concentrations on a Roche chemistry analyzer, and calculated LDL cholesterol. Correlation between these methods was poor for HDL (Passing-Bablok regression line: y = 30.31 + 0.853x) and could not be calculated for LDL. Automated HDL values were equal to, or higher than, the total cholesterol concentration in 25 of the 56 samples. The TG concentrations were above the reference interval in 18 samples, and these samples had an average of 96% of the cholesterol measured as HDL by the automated method, and 78% HDL by electrophoresis. Given that it is physiologically impossible to have more cholesterol within the HDL fraction than in the total serum fraction, and the increased proportion of TG found in LDL and very-low-density lipoprotein, our results draw into question the accuracy of the Roche automated assay in quantifying bovine lipoprotein fractions.

Abstract 425: Genetic Inhibition Of Hepatic Dolichol Biosynthesis Results In Hypolipidemia

Dolichol is a nonsterol isoprenoid derived from the mevalonate pathway. Dehydrodolichyl diphosphate synthase subunit (DHDDS) is a branch point enzyme that - in complex with Nogo-B receptor (NgBR) - catalyzes the first committed step of dolichol biosynthesis. Next, dolichol is phosphorylated, and used as carrier for oligosaccharides, which are transferred to nascent proteins in the N-linked glycosylation pathway. A growing body of evidence highlights the importance of N-linked glycosylation in regulating plasma lipid levels in humans. However, the underlying molecular mechanisms are largely unexplored. Therefore, the goal of this project is to define the role of dolichol biosynthesis in lipid metabolism in the liver, the major organ for the biosynthesis and clearance of lipoproteins. We used Adeno-Associated Virus (AAV)-mediated delivery of CRISPR/Cas9 (AAV-CRISPR) to delete Dhdds in mouse liver, to inhibit the hepatic biosynthesis of dolichol. Mice were injected with AAV-CRISPR or saline as control, and fed a high-fat diet for 4 to 12 weeks. Surprisingly, Dhdds liver-specific knockout (LSKO) mice gained less weight compared to control mice. Plasma total cholesterol and triglyceride levels were also reduced over time in Dhdds LSKO mice. Moreover, we observed less cholesterol content in the high-density lipoprotein (HDL) fractions as well as less triglycerides in very-low-density lipoproteins (VLDL). At the cellular level, Dhdds LSKO mice showed hepatic endoplasmic reticulum (ER) stress and decreased N-linked glycosylation. In addition, we observed significant downregulation of Sterol Regulatory Element-Binding Protein 1c ( Srebp-1c ) - a key regulator of de novo lipogenesis (DNL) - and downstream-regulated genes in the DNL pathway. Conversely, the expression of genes regulating cholesterol biosynthesis was unaffected. Taken together, our data show an important role for hepatic dolichol biosynthesis in regulating plasma lipids, potentially through modulation of Srebp-1c expression and DNL.

Simple and Sensitive Method for the Quantitative Determination of Lipid Hydroperoxides by Liquid Chromatography/Mass Spectrometry.

Lipid hydroperoxides (LOOH) are the initial products of the peroxidation of unsaturated lipids and play a crucial role in lipid oxidation due to their ability to decompose into free radicals and cause adverse effects on human health. Thus, LOOHs are commonly considered biomarkers of oxidative stress-associated pathological conditions. Despite their importance, the sensitive and selective analytical method for determination is limited, due to their low abundance, poor stability, and low ionizing efficiency. To overcome these limitations, in this study, we chemically synthesized eight fatty acid hydroperoxides (FAOOH), including FA 18:1-OOH, FA 18:2-OOH, FA 18:3-OOH, FA 20:4-OOH, FA 20:5-OOH, FA 22:1-OOH, FA 22:6-OOH as analytes, and FA 19:1-OOH as internal standard. Then, they were chemically labeled with 2-methoxypropene (2-MxP) to obtain FAOOMxP by one-step derivatization (for 10 min). A selected reaction monitoring assisted targeted analytical method was developed using liquid chromatography/tandem mass spectrometry (LC-MS/MS). The MxP-labelling improved the stability and enhanced the ionization efficiency in positive mode. Application of reverse-phase chromatography allowed coelution of analytes and internal standards with a short analysis time of 6 min. The limit of detection and quantification for FAOOH ranged from 0.1–1 pmol/µL and 1–2.5 pmol/µL, respectively. The method was applied to profile total FAOOHs in chemically oxidized human serum samples (n = 5) and their fractions of low and high-density lipoproteins (n = 4). The linoleic acid hydroperoxide (FA 18:2-OOH) and oleic acid hydroperoxide (FA 18:1-OOH) were the most abundant FAOOHs in human serum and lipoproteins. Overall, our validated LC-MS/MS methodology features enhanced detection and rapid separation that enables facile quantitation of multiple FAOOHs, therefore providing a valuable tool for determining the level of lipid peroxidation with potential diagnostic applications.

Arylesterase activity of paraoxonase 1 in patients with primary hypertension

Abstract Introduction Paraoxonase 1 is an enzyme associated with high-density lipoprotein fraction and is considered to present antioxidant activity. Objectives The aim of the study was to assess the arylesterase activity of paraoxonase 1 (PON1) in the serum of patients with hypertension, due to effect of therapy and before treatment. Patients and Methods. The study was conducted in 76 patients with primary hypertension and 28 volunteers for the control group. Hypertensive subjects were assigned to one of three groups: well controlled (n=25), poorly controlled (n=26), and newly diagnosed before therapy (n=25) hypertension. We evaluated metabolic parameters in all participants using routine laboratory methods, as well as arylesterase activity of PON1. Results The four study groups differed with arylesterase activity of PON1 and the highest levels were found in patients with well controlled hypertension and the lowest in newly diagnosed. All patients diagnosed with hypertension presented negative correlations between PON1 and systolic and diastolic blood pressure. Conclusions Effective treatment of hypertension could result in increased PON1 activity, despite unfavorable homocysteine concentrations in blood. Untreated hypertension might decrease activity of PON.

Anti-SARS-CoV-2 mRNA vaccines as inducers of humoral response against apolipoprotein A-1?

BackgroundCOVID‐19 and some anti‐SARS‐CoV‐2 vaccines trigger a humoral autoimmune response against a broad range of endogenous components, which may affect recipients’ prognosis in predisposed individuals. Autoantibodies directed against apolipoprotein A‐1 (AAA1 IgG) the major protein fraction of High Density Lipoprotein have been shown to be raised in COVID‐19 and in rheumatoid arthritis (RA) patients and other populations where they have been associated with poorer outcomes. We wanted to assess the impact of anti‐SARS‐CoV‐2 mRNA‐based vaccination on AAA1 autoimmune biomarkers in RA patients.Methods20 healthy controls and 77 RA mRNA‐based vaccinated patients were collected at baseline, 3 weeks after the first vaccination, 2 and 8 weeks after the second vaccination. AAA1 and SARS‐CoV‐2 serologies were measured by immunoassays. Systemic and local symptoms occurring during the vaccination protocol were recorded.ResultsmRNA‐based vaccination induced a significant increase in median AAA1 IgG levels in both healthy controls and RA patients overtime. However, in both populations, these medians trend did not translate into significant increase in AAA1 IgG seropositivity rates despite evolving from 5 to 10% in healthy controls, and from 9 to 12.9% in RA patients. No associations were retrieved between AAA1 IgG and symptoms of any kind during the vaccination protocol.ConclusionsmRNA‐based vaccination seems to induce a light AAA1 IgG response in immunocompetent individuals within 2 months after the last injection. Although we did not observe any warning signs, the formal demonstration of the harmlessness of such biological warrants further studies.